One of the most important garden investments we can make is in building healthy fertile soil, which doesn’t happen overnight, or in a single fell swoop, but is instead an ongoing process throughout the year. And while yards with extremely poor soil may benefit from the purchase and application of large amounts of topsoil, for the most part it’s possible to build and feed the soil with free or low-cost materials that are often in abundance locally.
In conjunction with a good compost pile, the addition of quantities of organic materials to the soil in the form of mulch or compost can do wonders for a backyard garden. Many times, materials that are considered waste by their source (i.e. spoiled hay, coffee grounds, spent grains from a brewery, yard clippings, etc.) can be had for free, just for the act of hauling them away, and with a little bit of time spent processing the materials into compost piles or top-dressing the garden beds, a regular supply of nutrients is made available to your plants.
Here’s a great introduction into the practice of building healthy garden soil with free resources: